[R] logistic regression

[Melrose2012]

I am trying to plot the logistic regression of a dataset (# of living flies
vs days the flies are alive) and then fit a best-fit line to this data.

Here is my code:
plot(fflies$living~fflies$day,xlab="Number of Days",ylab="Number of Fruit
Flies",main="Number of Living Fruit Flies vs Day",pch=16)
alive <- (fflies$living)
dead <- (fflies$living[1]-alive)
glm.fit <- glm(cbind(alive,dead)~fflies$day,family="binomial")
summary(glm.fit)
lines(sort(fflies$day),fitted(glm.fit) [order (fflies$day)],col =
"red",lwd=2)
lines(glm.fit,col = "red",lwd=2)

My problem is that, while I am pretty sure that I did the 'glm' command
correctly, when I try to plot this as a best-fit line on my data, it does
not fit (clearly on a different scale somehow).

Can anyone enlighten me about what I am doing wrong?  Should I be scaling
one of these somehow?  I've tried various types of scaling but nothing plots
the line on top of the plot (no matter which I scale).

Thanks so much for whatever help you can give me!

Cheers,
Melissa  

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